Archived filter change-no pressure-LP good

[Ncostello]

Geez... swapping out a new fuel filter is fast becoming something I dread. The first time I did it I found out my lift pump was dead... or maybe so I thought. It wouldn't even fill the cannister. When I installed my new one 4000 miles ago it did prime OK and I was finally able to start my truck.



Now 4000 miles after my new lift pump, I decided it was time to change the fuel filter. In the last 75 miles, its seems like the power is dropping off and the idle is getting about 100 rpm lower. The new lift pump has always idled 16psi and wont drop below 12psi at full throttle so I'd say its still healthy. Plus my key-on pressure without start up goes 15psi instantly. I figured this filter change would be simple and may solve my little problem.



I installed a new Fleetguard last night, took my time and inspected things completely. I didn't fill the cannister because I thought thats the job of the lift pump. Bumped the starter and it went straight to 15psi and ran for 30 seconds or so. While it was running I had my eyes glued to the mechanical pressure gauge. I'm thinking all is good at this point. After the lift pump stopped all was quiet (garage at night). Then all of a sudden I plainly hear what sounds like fuel being dumped back into the tank. Not a trickle sound but more like someone dumped a gallon all at once in the tank... kinda made a low rumble like sound. I open the tank thinking its either pressurized or has a vacuum but taking off the cap reveals neither.



I then bump the starter for the 2nd time and now 1psi on the gauge. Again and again, all I get is 1-2 psi. It wont prime. I loosened the banjo at the VP and got a few foamy bubbles and finally a full flow stream free of air during all subsequent LP cycles... but I cannot get the pressure beyond 1-2psi. I made a special rubber flat cap for the tank opening and put about 5psi regulated air to it hoping to assist the LP. It took off once like it was building pressure well... then no sooner than that happened it dropped off again and I heard that weird sound from the tank (sound came after I bled off the air from the tank). I also checked along time ago and my vent cap is removed from the tank pickup assy. Seems putting a little pressure to the tank is of no help. But maybe that puts pressure on the return line also and cancels itself out.



So now I refuse to start the truck because I know it will run for 5 seconds then die... thats when I get real mad!!! I have no idea. I think I need to remove the tank and see what the heck is going on in there. Something wont let the LP do its job... . way too much resistance to flow in there. Maybe the pickup screen is covered in crap or ??? Changing fuel filters is becoming a two day job for me.

 

[lschultz]

Strange. My son has 99 with about 130000 and fuel filter has been changed every 10000 and he has not had any problems. Any cracks in your lines anywhere,all the fittings tight. I'm sure someone will get on here that can help you.

 

[Ncostello]

I've about had it. Its still just a little fun however. I'm taking the bed off to get to the tank and I'm getting to the bottom of this whole thing. I'll pull the tank too and have it cleaned. I'm gonna check the whole pickup assy and modify it if I dont like what I see. Then I'm getting some hi-flow wildcat oversize banjos (5) and running 3/8" line everywhere I can... total replacement. Plus I'm finally moving my LP down low to the frame. And I'm getting a new fuel cap just in case. Maybe a new cannister housing. That should just about do it. This thing simply wont take prime at all. Plus I have a full tank to assist. Maybe its a good thing because now I'm forced to do some stuff I've been waiting to do.

 

[Joe Mc]

Neil,



I too have had moments with changing fuel filters. What I've had to do (if I didn't fill the canister) is loosen 3 fuel injector nuts (about 1/2 to 3/4 turn on the head) loosen the first then skip one etc. Then have somone crank the pi_s out of it until you get clear (no bubbles) fuel out of the nuts. Don't be frightened it may actually start up, if it does turn it off. This operation can be done by yourself if you have a remote started button. As the fuel clears stop cranking tighten nut on the one that cleared and repeat till all are clear. If you haven't worn down your battery it should fire up, probably run a bit rough at first till all the air clears out of the injectors etc.



Taking off the bed and droping your tank is a great deal of work especially if it isn't required. MHO + $. 02. Your call though.



Hindsight - It pays to fill the canister - if you don't - indeed the LP will fill it with fuel but inturn push air into the VP and injectors. Not fun!



Let us know how you make out.



Hope this helps - it's worked for me in the past good luck

 

[Ncostello]

Thanks for the tips Joe Mc. I havent tried to start it yet. If I do I know it will die much sooner than Saddam Hussein will. Thats what I'm trying to prevent... getting air in the injection lines and injectors. Unless I'm mistaken, running the LP three or four times after a filter change should only purge introduced air back to the fuel tank and not through the entire injection system. Isn't that what the VP return line does? I'm thinking when the VP44 starts spinning during cranking, thats when the air is injected into the lines... and thats when I need to start bleeding the injectors. I could be wrong.



I have set my mind to looking at the pickup assy and upgrading the fuel lines, fittings etc. I need to solve this dillema once and for all and the problems I'm having at each change are unacceptable to me. This process should be cut and dry... 20 minutes max. Instead its something I dread and wont do unless I dont need to drive it. Plus... filling the cannister with fuel then trying to fish the whole thing down through all the wires and cables in the way would be a mess at best for me. I think dry installing is the best way to go. Plus I should be able to do this if I'm stranded on the highway all alone with a clogged filter.

 

[CumminsAholic]

Even if you do get some air in the lines it'll still start. Just hold the throttle to the floor til it starts. The air that gets in some of the lines will clear out, just think how much air gets in when you put in different injectors. I never bled mine after my injector install, and it started fine. IMO, pretend it's a chev 6. 2 when it's cold out... . hold it to the rugs til it starts, just don't crank for minutes on end.

Corey

 

[Ncostello]

911's over here. I finally gave up trying to prime the LP to produce its normal 15psi... only 1-2psi was showing on the gauge. I just got in, cranked it for 3 seconds... nothing. Half throttle applied, 5 seconds of cranking and she took off fine without even running rough. Look at the pressure gauge and its buzzing away at 15psi.



Maybe I had a slight air lock in the LP that caused it to not prime. Who knows. But either way, I'm redoing my fuel lines all the way to the tank... and I have already made up my mind to remove the tank. I'll take some good photos of this work. Already had some good conversation with Wildcat Diesel about some custom AN style fittings (45's, 90's etc) they are about to market that have the correct 12mmx1. 5 swivel male thread on them. No adapters needed. They said they will be 8AN. Maybe too big for me. I'd take some 6AN About three weeks they will be available. Thats another story. Thanks everyone.